In this R03 application, we propose to study the safety and efficacy of vagal nerve stimulation (VNS) delivered through implantation of the NeuroCybemetic Prosthesis (NCP) System on bulimic behaviors in 10 female patients with severe, treatment-resistant bulimia nervosa. Current treatments have disappointing efficacies with 20 percent to 50 percent of patients still symptomatic at 5 year follow-up. A long illness duration and high frequencies of vomiting are associated with the poorest prognosis. Multiple lines of evidence converge to suggest that abnormal vagal neurotransmission may play a causative role in driving the bulimic behaviors. In this application, we propose that the use of the implanted NCP system as a vagal nerve pacemaker will provide enhanced control over vagal activity and thereby increase the number of patients achieving total abstinence. Additionally, we propose to conduct longitudinal measures of functional vagal activity in these patients across the clinical trial. We have obtained a FDA IDE and IRB approval to conduct this study. The proposed study would constitute the first use of the NCP for treatment of an eating disorder, specifically bulimia nervosa. If this initial pilot study finds this intervention to be both safe and effective in this small sample, then a larger, multicenter study would be warranted. The forthcoming results on physiological changes in vagal function will provide preliminary insights into the relationship between stimulation parameters, physiological changes, and symptom improvement. Collectively, the data collected during this study may lead to both the development of an enhanced treatment and novel insights into the pathophysiology of severe, treatment-resistant bulimia.